Impregnated fibrous materials and process of making the same



United States Patent Office 3,533,902 Patented Get. 13, 1970 3,533,902IMPREGNATED FIBROUS MATERIALS AND PROCESS OF MAKING THE SAME Richard C.Hoch, Wayland, Mass., assignor to W. R.

Grace & Co., Cambridge, Mass., a corporation of Connecticut No Drawing.Continuation of application Ser. No.

451,342, Apr. 27, 1965. This application May 29,

1969, Ser. No. 833,849

Int. Cl. D04h 1/50 US. Cl. 161--170 2 Claims ABSTRACT OF THE DISCLOSUREAn impregnated fibrous material particularly suitable for use as asynthetic leather which is comprised of a compressively shrunk nonwovenweb of textile length synthetic fibers impregnated with an elastomericbinder. The web is preferably needled.

This application is a continuation of Ser. No. 451,342 filed Apr. 27,1965 and now abandoned.

This invention relates to a synthetic leather or coating base materialcharacterized by a leather-like feel, resilience, and texture.

A number of substitutes for leather have come into general use. Suchmaterials include plastic films, coated fabrics, and coated or uncoatedpapers. Such materials are usually stronger, more abrasion resistant,more waterproof, and more resistant to flexing than leather and are alsogenerally more uniform in properties. Synthetic leathers are utilizedfor shoe uppers, leather coats, gaskets, gloves, slippers, luggage,brief cases, camera cases, handbags, and the like.

It has now been found that a novel synthetic leather structurecharacterized by improved flexibility, internal bonding strength,resilience, and reduced piping can be prepared which comprises anextensibilized, preferably a biaxially-extensibilized, nonwoven web ofsnythetic fibers which has been impregnated with a polymeric bindermaterial.

Extensibilizing or compressive shrinking of webs is known to the art.US. Pats. Nos. 2,624,245; 3,122,469; and 3,055,496 are directed tocellulosic webs which have been compressively shrunk and to apparatusfor accomplishing the shrinkage. It has now been found that a superiorproduct can be prepared by compressively shrinking a nonwoven web oftextile length snythetic fibers.

The compressive shrinking of the web is carried out prior (toimpregnation, after impregnation but while there is still moisture inthe fiber, e.g., about 20 to 30%), or on the dried, impregnated web.Preferably, the compressive shrinking is accomplished after theimpregnation of the nonwoven web while the web has a moisture content ofabout 25%. However, improvements in flexibility,

denier ranges from 0.5 to 15 denier per filament, preferably l to 6.

The nonwoven web may be prepared by methods known to the art, forexample, by air laying equipment or by normal paper-making equipmentsuch as Rotoformer or Fourdrinier machines. The nonwoven webs areemployed in the form they come off the web-making equipment, oralternatively, they are pressed to increase the density. The weight ofthe nonwoven webs ranges from 1 to 20 ounces per square yard, preferably6 to 10 ounces per square yard. If drying of the webs is desired,conventional methods are employed.

After the formation of the nonwoven web, it is preferably needled withbarbed needles in order to lock the fibers together and substantiallyincrease the internal bonding strength of the web. More preferably, thenonwoven web is needled on both sides. The degree of needling isdetermined by the internal bonding strength desired in the web; thegreater the degree of needling, the greater the internal bonding of theWeb. Preferably, about 15 passes on each side of the web is carried outwith conventional needling devices. It should be understood that whilethe needling step is a preferred embodiment, the nonwoven web may befurther processed without needling.

The nonwoven webs are provided with additional internal bonding strengthby means of polymeric binder materials known to the art. The preferredbinders are polymeric elastomers having high adhesion to the fiber, aminimum elongation of 400%, a minimum tensile strength of 50 p.s.i., anda maximum modulus of elasticity of 1000 psi. Particularly preferredbinders are carboxylic butadiene-containing copolymers. In a preferredembodiment a small amount, e.g., 5% or less, of a Wet strength resinsuch as phenol formaldehyde or melamine formaldehyde was also employed.The level of impregnation of the polymer on the fiber ranges between 50and by weight based on the weight of the fiber.

As examples of suitable impregnating binders, mention may be made ofnatural and synthetic rubbers such as butadiene/styrene, copolymers,butadiene/acrylonitrile copolymers, neoprene, and the like. Othersaturants are described in the following United States patents:2,410,078; 2,416,232; 2,438,195; 2,441,523; 2,692,253; 2,760,884;2,799,596; 2,848,105; 2,848,344; 2,899,353; 2,905,584; and 2,837,109.

The impregnating compositions may also employ antioxidants, fillers,thickeners, curing agents, and the like. The impregnating materials areemployed in both the cured and uncured state. Preferably, the polymericmaterials are employed as latices or water dispersions. Solventsolutions and melts may also be used.

The nonwoven web may be impregnated by conventional means. If the web isformed by air laying methods or other dry methods, it may be impregnatedin the dry state. If it is formed by Wet, paper-making techniques, itmay be saturated Wet as it comes off the paper rnaking machine or firstdried and then saturated. Preferably, the web is formed by air-layingmethods, and the dry web is saturated.

The compressive shrinking is accomplished by compacting and rearrangingthe fibers through compression of the web between two complementarysurfaces. One of the surfaces at the time of contacting the web is anexpanded elastic adherent surface and the other is a stable nonadherentsurface such as a steel bar or roll. After being gripped between the twosurfaces, the elastic surface is caused to contract which results inshrinkage of the web. This shrinkage is best carried out at a Webtemperature in the range of 210 to 300 F. and under sufiicientcompression perpendicular to the surfaces of the Web to pre- 3 vent morethan a 5 percent increase in the thickness of the impregnated web.

The Webs are compressively shrunk in a single direction by one passthrough the compressive shrinking machine in one direction, or the Websmay be compressively In all cases the fibers used were 1%; inches inlength and 6 denier/filament. In Examples 1 to 29 the web Weight was 5ounches per square yard and the impregnant was a 67/33butadiene/acrylonitrile copolymer latex. I11 Examples 31 to 37 theimpregnating composition comshrunk in two dire tion th hi di ti (MD) 5prised 98% carboxylicbutadiene-medium nitrile c0- and in the direction.perpendicular to the machine direc- P y and 2% Phenol formaldehyderesin- In hoh, 1.6,{1'16 cross-direction (CD). Shrinkage in two diamples31, and 32 the Web weight prior to impregnarections is accomplished bypassing the web through the tiOn Was 9 Ounces P Square y In Examplesapparatus described in US. Pat. No. 2,624,245 in one di- 10 and 35 theWeb Weight Prior to impregnation Was 7 Ounces rection, turning the web90 and again passing it through Pe Square y In EXaInPIeS 36 and 37 theWeb Weight the apparatus or by a single pass through the device de- P toimpregnation Was 14 Ounces P Square y scr bed 111 US. Pat. No. 3,122,469which compressively In all the eXamples impregnation was carried out onshrinks the webs in both the machine and cross-direction h dry Web Priorto compressive Shrinking- The iInPregnaat the Same ti Th di l f p 15tion level is weight percent of impregnant based on the 2,624,245; 96; ad 3,122,469 are incorporated. eight of fiber (solids on solids). Thethickness is reherein to the t t li bl ported on the compressivelyshrunk material.

After the nonwoven web has been impregnated and In the following tablerefers to an compressively h k, i may b employed in that f pregnated webwhich has been dried to a moisture level as synthetic leather. In apreferred embodiment, however, of ,about refers to an impregnated Webthe material is laminated to a fabric, preferably a woven Whlch wasdried to a level of less than 5% and then fabric, to provide dimensionalstability. The impregnated, Wet to a level of about 25% Prior tocompressive Shrinkcompacted material is also preferably coated with arefers to impregnated Webs which have a polymeric material to simulatethe finish of leather. molsture Content of about 5% of less- Preferably,th ti i f a fl ibl type such as a 25 Control samples, i.e., materialswhich were not subpolyurethane, plasticized polyvinyl chloride, or acar- Jeeted t0 the compressive Shrinking Operation, e150 boxylicbutadiene-acrylonitrile copolymer to provide a h e for Comparative P pmaterial with a scuff resistance greater than leather, high Plplng isthe development of Wrinkles in the Specimen water resistance, and amoisture vapor permeability of When it is Pressed around mandrel- Thefigure reported greater than 1000 grams per 100 square meters per h isthe smallest mandrel radius around which the specimen Table 1illustrates synthetic leather constructions within can be e Wlthontwrinkling the sco e of th present invention d h properties fDelamination resistance is the force, expressed in units such materials.In the following nonlimiting examples, of Ph P 1neh 0t Width, requiredto Continue the the needled webs were processed on a needle loommanusphttlng of e SPeCIInen into epp y tWO equal factured by the JamesHunter Machine Company using P TWO speennens 10 X 1 two strips of mhind- Torrington needles 15 x 18 x 36 x 3 /2 CB. Fifteen passes lng t p9 In length, are Placed that pp y on the needle loom were made on bothsides of the web of P p extends beyond each end of the P The in thefollowi manner; specimens are pressed for 30 seconds at 275 F. and 5 psiwith about 0.5 in. of tape extending beyond the 40 edge of the press.The two free ends of the tape are pulled until the specimen starts toseparate into two approxi- No of ass eg 'm Depth 29 mately equal plies.The two free ends of the tape are p 5 ,332, fi gi gt then placed in thejaws of an Instron Tester, and the machine was run at 10 inches/minute.

% 45 Gurley Stiffness is a measure of the force required to 7 bend aspecimen through a certain angle. Stiffness was determined on a GurleyR. D. Stiffness Tester.

TABLEI Impreg- Percent Compressive shrinking Pipin Gurley Stiit-Delanii- Ex. nation shrink, Thickness (in. ness mgms, nation No FiberNccdlccl (percent) MD CD Semi-dry Re-wct Dry (mils) MDXCD MDXCDresistance Mxo 447x427 6x0 466x846 1,057x2,325 0x0 730x766 /xo 605X890 11,467X1,378 0 0 399x570 0 0 534x542 837X1,467 0X0 795x534 0x0 433x445 11, 673 2, 033 0x0 570 1,004 0x0 539x445 0 534x344 0X0 235x256 0x0333x306 751X648 0 0 427x402 0x0 452x310 l 676 0X0 6l2 506 0x0 516x333 00 534x533 1,2s3x733 0 0 1,210 1, 121 0 0 880X972 3,072 3,355 0 0 622x3540x0 334x420 623x633 0X0 3, 378X3, 845 3X3 12, 278X15,824

It will be noted from the data in Table 1 that the impregnated webswhich have been compressively shrunk have superior delaminationresistance, less piping, and better flexibility than correspondingimpregnated webs which have not undergone the compressive shrinking. Itwill also be noted that improvements in flexibility, piping, anddelamiantion resistance are achieved in nonwoven webs which have notbeen needled prior to compressive shrinking. However, as stated above,the preferred materials are needled to provide higher internal bondingstrength.

The materials of the present invention also possess reduced resilienceas compared with materials which are not compressively shrunk. Lack ofresilience is especially desirable in materials used for shoe uppers.This property can be measured by folding the material back on itself andobserving how quickly the material recovers to the unbent position.Materials of the present inveniton possess substantially less recoverythan prior art materials.

By means of the compressive shrinking operation, the web is reduced inthickness and the density is increased to some degree. A higher internalbonding strength is achieved in the materials of the present inventionwith the use of less elastomeric binder. The less binder in the web, themore porous the material will be and the more absorbent the fibers willbe. These two factors result in a more comfortable shoe upper material.These advantages are gained without the loss of internal bondingstrength occasioned by the decreased amount of binder in the web.

It is claimed:

1. An impregnated fibrous material particularly suited for use assynthetic leather consisting of a compressively shrunk nonwoven web ofsynthetic fibers having a length of from /2 to 3 inches, said web havinga moisture content of about 25% prior to compressive shrinking, andbeing impregnated with an elastomeric binder material at a level ofbetween and by weight based on the weight of said fibers.

2. The process for preparing a fibrous impregnated material particularlysuited for use as synthetic leather which consists of impregnating anonwoven web of synthetic fibers which have a length of from /2 to 3inches with an elastomeric binder to a level of about 50-150% by weightbased on the weight of the fibers and compressively shrinking theimpregnated web, the web having a moisture content of about 25% prior tocompressive shrinking.

References Cited UNITED STATES PATENTS 2,881,505 4/1959 Hoffman 28-72.23,245,863 4/1966 Sonnichsen et a1. 16172 3,317,335 5/1967 Marrinan eta1. 2872.2 X

ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant'Examiner US.Cl. X.R.

ll7140; 15684; l62206

